1. Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, University of Ghent, Salisburylaan 133, B-9820 Merelbeke, Belgium
2. Delft Diagnostic Laboratory, R. de Graafweg 7, 2600 GA, Delft, The Netherlands
3. Department of Food and Environmental Hygiene, Faculty of Veterinary Medicine, University of Helsinki, PO Box 57, 00014 Helsinki, Finland
4. Department of Microbiology, Faculty of Sciences, University of Ghent, Ledeganckstraat, B-9000 Ghent, Belgium